Conventional softballs have one of four different types of covers, namely full grain leather stitched covers, coated split leather stitched covers, synthetic stitched covers, or molded covers. Stitched covers customarily are formed from two separate pieces of leather or synthetic material which exhibit the traditional interfitting dumbbell configuration and are fastened together with herringbone stitching. The stitching forms ridges which enhance the gripping characteristics and desired aerodynamic properties of the ball.
Genuine leather traditionally has been deemed to be the best cover material due to its softness, texture and durability. Such material provides a firm but relatively soft cover that advantageously provides for potentially increased spin off of the bat, which can produce additional carry and lift, which in turn results in increased hitting distance. Furthermore, a leather-covered ball produces a solid crack-type sound when struck with a bat. This sound is not replicated by many synthetic ball covers.
All conventional softball cover materials are found to reduce the coefficient of restitution (C.O.R.) of the ball to a limited extent. However, leather traditionally has been found to result in a smaller reduction in coefficient of restitution of the ball than results from the use of synthetic or molded covers.
Synthetic leather softball covers typically are formed of polyvinyl chloride (PVC). While PVC covers have good resistance to wear and moisture, it is necessary to make such covers thicker than leather in order to obtain comparable durability and stitchability. Unfortunately, the thicker covers tend to dampen the sound when the bat hits the ball, thereby losing the solid crack players have come to expect, and also result in a greater reduction in the coefficient of restitution of the ball as compared to balls with thinner leather covers.